Methods and apparatus for renal neuromodulation

Abstract

Methods and apparatus are provided for renal neuromodulation using a pulsed electric field to effectuate electroporation or electrofusion. It is expected that renal neuromodulation (e.g., denervation) may, among other things, reduce expansion of an acute myocardial infarction, reduce or prevent the onset of morphological changes that are affiliated with congestive heart failure, and/or be efficacious in the treatment of end stage renal disease. Embodiments of the present invention are configured for percutaneous intravascular delivery of pulsed electric fields to achieve such neuromodulation.

We claim: 
     
       1. A method for monitoring renal neuromodulation, the method comprising:
 advancing a catheter into a vessel of a patient, the catheter comprising a distal section and a plurality of electrodes at the distal section; 
 applying a stimulation electric field to a tissue of the patient; 
 monitoring a physiologic response to the stimulation electric field indicating in the tissue the presence of a neural fiber that innervates a kidney; and 
 applying a denervating electric field to the neural fiber via the catheter to inhibit neural activity along the neural fiber, 
 wherein the denervating electric field is applied when the distal section of the catheter is in a helical configuration apposing an interior wall of the vessel. 
 
     
     
       2. The method of  claim 1 , wherein the vessel comprises a renal artery. 
     
     
       3. The method of  claim 1 , wherein the vessel comprises a branch of a renal artery. 
     
     
       4. The method of  claim 1 , further comprising varying the pitch of the helix of the distal section of the catheter while the distal section is in the helical configuration. 
     
     
       5. The method of  claim 1 , wherein the electrodes are dynamically assignable. 
     
     
       6. The method of  claim 1 , wherein advancing a catheter into a vessel of a patient comprises delivering the catheter to the vessel in a low profile delivery configuration. 
     
     
       7. The method of  claim 6 , wherein the vessel comprises a renal artery. 
     
     
       8. The method of  claim 6 , further comprising positioning the catheter within the vessel and actively expanding the catheter once the catheter has been positioned within the vessel. 
     
     
       9. The method of  claim 1 , wherein the electrodes at the distal section of the catheter are used both to apply the stimulation electric field and to apply the denervating electric field. 
     
     
       10. The method of  claim 1 , wherein applying a stimulation field and monitoring a physiologic response comprise applying a stimulation field and monitoring a first physiologic response prior to applying a denervating electric field and applying a stimulation field and monitoring a second physiologic response after applying the denervating electric field. 
     
     
       11. The method of  claim 10 , further comprising comparing the first physiologic response and the second physiologic response to determine an extent of renal neuromodulation. 
     
     
       12. The method of  claim 1 , wherein applying a denervating electric field comprises ablating the neural fiber. 
     
     
       13. The method of  claim 1 , wherein applying a stimulation electric field comprises stimulating afferent renal nerve fibers. 
     
     
       14. The method of  claim 1 , wherein applying a stimulation electric field comprises stimulating efferent renal nerve fibers. 
     
     
       15. The method of  claim 1 , wherein applying a stimulation electric field comprises intravascularly delivering the stimulation electric field. 
     
     
       16. The method of  claim 15 , wherein applying a stimulation electric field further comprises modulating at least one of frequency, amplitude and pulse duration of the stimulation electric field to facilitate passage of the electric field to the tissue. 
     
     
       17. The method of  claim 1 , wherein monitoring a physiologic response to the stimulation electric field comprises monitoring at least one of renin, sodium, and blood pressure. 
     
     
       18. The method of  claim 1 , wherein monitoring a physiologic response to the stimulation electric field comprises monitoring a reduction in renal blood flow. 
     
     
       19. The method of  claim 1 , further comprising identifying an optimal location for renal neuromodulation based on the monitored physiologic parameter. 
     
     
       20. The method of  claim 1 , wherein the stimulation field is a first stimulation field, and wherein the method further comprises applying a second stimulation field to the tissue and monitoring the absence of a physiologic response following inhibiting neural activity along the neural fiber. 
     
     
       21. A method for monitoring effectiveness of renal neuromodulation, the method comprising:
 applying a stimulation electric field to renal nerves; 
 monitoring a change in renal blood flow in response to the stimulation electric field; and 
 delivering an energy field to the renal nerves via an intravascularly positioned catheter comprising a distal section having a helical configuration and a plurality of electrodes at the distal section, 
 wherein the energy field inhibits neural activity along the renal nerves. 
 
     
     
       22. The method of  claim 21 , further comprising varying the pitch of the helix of the distal section of the catheter while the distal section is in the helical configuration. 
     
     
       23. The method of  claim 21 , wherein the electrodes are dynamically assignable. 
     
     
       24. The method of  claim 21 , wherein advancing a catheter into a renal artery of a patient comprises delivering the catheter to the renal artery in a low profile delivery configuration. 
     
     
       25. The method of  claim 24 , further comprising positioning the catheter within the renal artery and actively expanding the catheter once the catheter has been positioned within the renal artery. 
     
     
       26. The method of  claim 21 , wherein the electrodes at the distal section of the catheter are used both to apply the stimulation electric field and to apply the denervating electric field. 
     
     
       27. The method of  claim 21 , wherein monitoring a change in renal blood flow comprises monitoring the velocity of blood flow through the renal artery. 
     
     
       28. The method of  claim 27 , wherein monitoring the velocity of blood flow through the renal artery comprises monitoring blood flow velocity using a Doppler ultrasound sensor. 
     
     
       29. The method of  claim 21 , wherein monitoring a change in renal blood flow comprises monitoring the flowrate of blood flow through the renal artery. 
     
     
       30. The method of  claim 29 , wherein monitoring a change in renal blood flow further comprises monitoring the flowrate prior to stimulation to determine a baseline flowrate, monitoring the flowrate after stimulation and comparing the flowrate after stimulation to the baseline flowrate. 
     
     
       31. The method of  claim 21 , wherein monitoring a change in renal blood flow comprises visually monitoring a change in renal blood flow. 
     
     
       32. The method of  claim 31 , wherein visually monitoring a change in renal blood flow comprises visualizing renal blood flow using an external ultrasound transducer. 
     
     
       33. The method of  claim 21 , wherein monitoring a change in renal blood flow comprises monitoring renal blood flow via a pressure transducer. 
     
     
       34. The method of  claim 21 , wherein monitoring a change in renal blood flow comprises measuring travel time lag of an intravascular temperature input. 
     
     
       35. The method of  claim 21 , wherein delivering an energy field to the renal nerves comprises ablating the renal nerves via the energy field.